Molecular mechanism of transcriptional regulation by insulin

我们从18950+37核苷酸中获得了含有L丙酮酸激酶(LPK)基因5‘侧翼区的转基因小鼠，该基因含有一个增强子单元和与氯霉素乙酰转移酶(CAT)基因连锁的TATA盒作为功能元件。饲料中葡萄糖和果糖均能刺激转基因的表达。将融合基因导入培养的肝细胞，用胰岛素或不加胰岛素孵育肝细胞。胰岛素在葡萄糖存在的情况下刺激CAT基因的表达，但在丙酮酸存在的情况下不能。因此，我们认为LPK基因的一个增强子单位是胰岛素反应单位。HNF1与L-III结合，后者构成LPK基因的增强子单位。HNF1的表达不受饮食控制。通过CAT实验，我们发现葡萄糖激酶的5‘侧翼区域直到-1100包含了对胰岛素有反应的DNA区域。

We produced transgenic mice containing the 5'-flanking region of the L-type pyruvate kinase (LPK) gene from nucleotide -189 50 +37, which includes an enhancer unit and TATA box as functional elements, linked to the chloramphenicol acetyltransferase (CAT) gene. Transgene expression was stimulated by both dietary glucose and fructose in the liber. The fusion gene was also transfected into cultured hepatocytes and the cells were incubated with or without insulin. Insulin stimulated expression of the CAT gene in the presence of glucose, but not in the presence of pyruvate. Thus, we suggest that an enhancer unit of the LPK gene is insulin response unit.2. HNF1 binds to L-III, which constitutes an enhancer unit of the LPK gene. Expression of HNF1 was not under dietary control.3. Using CAT assay, we showed that the 5'-flanking region of the glucokinase up to -1100 contained the DNA region responsive to insulin.